Testing an electrical connection of a device cap

Abstract

A method of testing a device includes setting a potential of a cap terminal of the device to a first voltage, setting a potential of a self test plate of the device to a testing voltage, and detecting a first displacement of a proof mass of the device when the cap terminal is set to the first voltage and the self test plate is set to the testing voltage. The method includes setting a potential of the cap terminal of the device to a second voltage, detecting a second displacement of the proof mass of the device when the cap terminal is set to the second voltage and the self test plate is set to the testing voltage, and comparing the first displacement and the second displacement to evaluate an electrical connection between the cap terminal and a cap of the device.

What is claimed is: 
     
       1. A method of testing a device, the method comprising:
 setting a potential of a cap terminal of the device to a first voltage; 
 setting a potential of a self test plate of the device to a testing voltage; 
 detecting a first displacement of a proof mass of the device when the cap terminal is set to the first voltage and the self test plate is set to the testing voltage; 
 setting a potential of the cap terminal of the device to a second voltage; 
 detecting a second displacement of the proof mass of the device when the cap terminal is set to the second voltage and the self test plate is set to the testing voltage; and 
 comparing the first displacement and the second displacement to evaluate an electrical connection between the cap terminal of the device and a cap of the device. 
 
     
     
       2. The method of  claim 1 , wherein comparing the first displacement and the second displacement to evaluate the electrical connection between the cap terminal and the cap includes determining a difference between the first displacement and the second displacement. 
     
     
       3. The method of  claim 2 , including comparing the difference between the first and second displacement to a threshold value. 
     
     
       4. The method of  claim 1 , wherein the device is an accelerometer. 
     
     
       5. The method of  claim 1 , wherein the second voltage is the testing voltage. 
     
     
       6. The method of  claim 1 , wherein the first voltage is a voltage of the proof mass of the device. 
     
     
       7. A method of testing a device, the method comprising:
 detecting a first displacement of a proof mass of the device when a potential of a cap terminal of the device is set to a first voltage; 
 measuring a time period from when the potential of the cap terminal of the device is set to the first voltage to the first displacement of the proof mass is detected; and 
 comparing the measured time period to a threshold to evaluate an electrical connection between the cap terminal of the device and a cap of the device. 
 
     
     
       8. The method of  claim 7 , including:
 detecting a second displacement of the proof mass of the device when the potential of the cap terminal of the device is set to a second voltage; and 
 comparing the first displacement and the second displacement to evaluate the electrical connection between the cap terminal and the cap of the device. 
 
     
     
       9. The method of  claim 8 , including, before detecting a first displacement of a proof mass of the device, setting a potential of a self test plate of the device to a first self test voltage. 
     
     
       10. The method of  claim 9 , including, before detecting a second displacement of a proof mass of the device, setting a potential of a self test plate of the device to a second self test voltage. 
     
     
       11. The method of  claim 10 , wherein the second self test voltage is the same as the first self test voltage. 
     
     
       12. The method of  claim 8 , wherein comparing the first displacement and the second displacement to evaluate the electrical connection between the cap terminal and the cap includes determining a difference between the first displacement and the second displacement. 
     
     
       13. The method of  claim 12 , including comparing the difference between the first and second displacement to a threshold value. 
     
     
       14. A method of manufacturing a device, the method comprising:
 fabricating the device on a substrate, the device including a cap, a cap terminal, and a proof mass; 
 testing an electrical connection between the cap and the cap terminal by:
 detecting a first displacement of the proof mass of the device when a potential of the cap terminal of the device is set to a first voltage, 
 detecting a second displacement of the proof mass of the device when the potential of the cap terminal of the device is set to a second voltage, and 
 comparing the first displacement and the second displacement to determine whether the cap terminal and the cap of the device are electrically connected; and 
 
 when the cap terminal and the cap of the device are determined to be electrically connected,
 singulating the substrate, and 
 providing the device to a recipient. 
 
 
     
     
       15. The method of  claim 14 , including, when the cap terminal and the cap of the device are determined to be not electrically connected:
 discarding the device. 
 
     
     
       16. The method of  claim 14 , wherein comparing the first displacement and the second displacement to determine whether the cap terminal and the cap of the device are electrically connected includes determining a difference between the first displacement and the second displacement. 
     
     
       17. The method of  claim 16 , including comparing the difference between the first and second displacement to a threshold value. 
     
     
       18. The method of  claim 14 , wherein the device is an accelerometer. 
     
     
       19. The method of  claim 14 , including:
 when detecting the first displacement, setting a potential of a self test plate of the device to a self test voltage; and 
 when detecting the second displacement, setting the potential of the self test plate of the device to the self test voltage.